1. Field of the Invention
This invention relates generally to pistons and methods of construction thereof, and more particularly to piston molds and methods of construction therewith.
2. Related Art
It is known to construct a piston with an annular cooling gallery having an undercut located immediately radially inward of a piston ring belt. The undercut provides an overhanging portion of ring belt, which in turn presents complications in casting the piston. To avoid having to machine the undercut after casting, the mold cavity must include a projection or panel having a negative shape of the desired undercut configuration. However, in order to extract or remove the cast piston from the mold cavity, the panel must be removed completely from the undercut and the mold cavity. Because the depending ring belt is formed radially outward from the undercut, the panel cannot be simply moved radially outwardly in a purely horizontal direction from the undercut. To further complicate matters, pin bosses formed in the molding process that depend from the ring belt in laterally spaced relation from one another and flare laterally outwardly with respect to a central axis of the piston prevent the undercut forming panel from being moved downwardly in a purely vertical direction. Accordingly, to overcome this problem, many known mold assemblies include a panel that must be pivoted out of the mold cavity. However, the pivoting motion of the panel restricts the size of the available undercut that can be formed depending on the envelop dimensions of the mold cavity.